Apparatus for preparing spun yarn

ABSTRACT

Apparatus for preparing spun yarn comprising back rolls for feeding fiber from a supply thereof to front rolls spaced from the back rolls and serving to draft fiber received therefrom. A stretch breaking zone and a draft zone are arranged in succession in that order between the back rolls and the front rolls. An endless bottom apron extends between the back rolls and front rolls over the stretch breaking zone and the draft zone, and the bottom apron passes on respective support plates adjacent the back rolls and front rolls. Output rolls are mounted in the stretch breaking zone for drawing fiber from the back rolls and stretch breaking the fiber, and input rolls are provided in the draft zone for receiving fiber from the output rolls and for advancing the fiber to the front rolls. Both the input and output rolls include top and bottom rolls for advancing the fiber therebetween. The bottom apron extends on and is driven by the bottom rolls of the input and output roll means. A first top apron is mounted in the stretch breaking zone, and a second top apron is mounted in the draft zone, the first top apron passing on a further plate and on the upper roll of the output rolls in the stretch breaking zone and driven by the latter, the second top apron passing on a further plate and on the upper roll of the input rolls in the draft zone and driven by the latter. The first and second top aprons are opposed to the bottom apron to control the feed of the fiber therethrough.

United States Patent [191.

Nakano et al.

[ Feb. 5, 1974 1 APPARATUS FOR PREPARING SPUN YARN [73] Assignee: Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, Japan 22 Filed: Mar. 18,1971

21 Appl.No.: 125,524

Related US. Application Data [62] Division of Ser. No. 618,469, Feb. 24, 1967, Pat. No.

Primary Examiner-Dorsey Newton Attorney, Agent, or Firm-Waters, Roditi, Schwartz & Nissen [57] 7 ABSTRACT Apparatus for preparing spun yarn comprising back rolls for feeding fiber from a supply thereof to front rolls spaced from the back rolls and serving to draft fiber received therefrom. A stretch breaking zone and a draft zone are arranged in succession in that order between the back rolls and the front rolls. An endless bottom apron extends between the back rolls and front rolls over the stretch breaking zone and the draft zone, and the bottom apron passes on respective support plates adjacent the back rolls and front rolls. Output rolls are mounted in the stretch breaking zone for drawing fiber from the back rolls and stretch breaking the fiber, and input rolls are provided in the draft zone for receiving fiber from the output rolls and for advancing the fiber to the front rolls. Both the input and output rolls include top and bottom rolls for advancing the fiber therebetween. The bottom apron extends on and is driven by the bottom rolls of the input and output roll means. A first top apron is mounted in the stretch breaking zone, and a second top apron is mounted in the draft zone, the first top apron passing on a further plate and on the upper roll of the output rolls in the stretch breaking zone and driven by the latter, the second top apron passing on a further plate and on the upper roll of the input rolls in the draft zone and driven by the latter. The first and second top aprons are opposed to the bottom apron to control the feed of the fiber therethrough.

3 Claims, 6 Drawing Figures Patented Feb. 5, 1974 3,789,461

5 Sheets-Sheet Z APPARATUS FOR PREPARING SPUN YARN CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of co-pending application Ser. No. 618,469, filed Feb. 24, 1967 and now issued as U.S. Pat. No. 3,596,458.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spun yarn of an elastic fiber having excellent elastic elongation of more than 100 percent and a quick recovery from stretching to an elongation which is less than its breaking elongation, and a blended spun yarn of said elastic fiber with any of the known hard fibers. The invention also relates to an apparatus for producing same.

2. Prior Art Spandex is the first synthetic elastomeric fiber industrially utilized and is now used in the forms of bare yarn, covered yarn or core-spun yarn. However, the spandex fibers actually employed in these fields are all as filament yarns, and no spun spandex yarn has been developed up to now. Furthermore, most of the spandex filament yarns used in these fields are of fine-denier such as, for example, 140 d, 70 d and 40 d, and these fine-denier yarns are extremely expensive thereby preventing expansion of the market therefor.

SUMMARY OF THE INVENTION The invention is directed to a spun yarn consisting of 100 percent of an elastic staple fiber which has a breaking elongation of more than 100 percent, an elastic recovery from high stretching of more than 90 percent and a Youngs modulus of less than 0.5 g/d.

The invention is also directed to apparatus comprising a back roll, an intermediate roll and a stretchbreaking zone between said rolls wherein the improvement comprises top and bottom approns in the stretchbreaking zone, said aprons being driven at the same speed as the intermediate roll.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view of a direct spinning machine which is conventional.

FIG. 2 graphically shows the correlation between the distance (ho) from the back roll to the intermediate roll and the draft ratio of the spandex spun yarn prepared by using the apparatus as shown in FIG. 1.

FIG. 3 shows a part of a direct spinning machine equipped with a pair of endless approns and employed in the present invention.

FIG. 4 is a cross sectional view of the direct spinning machine particularly useful in the practice of the present invention.

FIG. 5 is a staple diagram representing the correlation between fiber length and content in the spun yarn of elastic fiber prepared by using the apparatus shown in FIG. 4.

FIG. 6 is a graph showing the correlation between the effective coefficient of fiber strength in yarn strength and the fiber number in cross section of yarn prepared by using an elastic fiber (a) or a hard fiber (b).

DETAILED DESCRIPTION A principal object of the present invention is to provide a cheap fine-denier spandex spun yarn. The market price of the coarser yarn of, for example, 3000 d or 5000 d is less than about one third the price of the above-mentioned finer yarn, and the price difference between the two was more than 5 dollars per pound as of August, 1966. Therefore, if it were possible to manufacture a finer yarn from this inexpensive coarser yarn with a reasonable spinning cost of, for example, less than one dollar per pound, it is beyond question that the market for spandex would be greatly expanded.

A second object of the present invention is to provide a single covered spandex yarn or core-spun yarn having greatly reduced kinking properties. A highly twisted spandex yarn tends to produce kinking due to the high elasticity thereof. Therefore, in the covered yarn technology, spandex is always supplied in the form of double covered yarn and no single covered yarn has yet been used. For the same reason, in preparing core-spun yarn, a steaming treatment has generally been used to prevent such kinking despite a lowering of the excellent elasticity resulting therefrom. T0 the contrary, the present spandex spun yarn, which is used to cover yarn or core-spun yarn, is twisted, in the spinning process, in a direction opposite that of the twists thereafter given in the core-spinning or covering process, so that this counter twist reduces, or makes negligible the kinking properties of core-spun yarn or single covered yarn under some conditions of twist multiplication.

A third object of the present invention is to provide a blended spun yarn of an elastic fiber and a hard fiber (natural or man-made fiber) with an optional blending ratio. Hitherto, the content of the elastic fiber in a blended spun yarn as far as has been reported to date is limited to the order of less than 30 percent as described in US. Pat. No. 3,007,227. Therefore, this novel blended spun yarn having no limitation in the blending ratio of elastic fiber affords a new kind of product and contributes towards rapid development of new markets for spandex fibers.

The aforesaid and other objects will become apparent to those skilled in the art from a consideration of the following specification, drawing and claims. The principle of the method is to employ a direct spinning system; i.e., a multifilament yarn or a tow of elastic fiber becomes spun yarn through the consecutive steps of breaking, drawing and twisting in one process.

In a conventional spinning system requiring a carding process such as the cotton spinning system, worsted spinning system, and modifications thereof, woolen spinning system etc., or in the conventional spinning system or the tow to top converter system requiring the drawing of thick slivers, it is impossible to make a pure spun yarn of umlimited fiber or blended spun yarn of elastic fiber with an ulimited blending ratio for the following reasons. In the first place, since very pliant elastic fibers are apt to adhere to the top end of the metallic wire, the carding action is poor. In the second place, in a drawing or roving process comprising drawing a sliver constructed of several thousands or several ten thousands of fibers, it is difficult to pick up a single fiber out of the sliver and to separately draw away each fiber, because frictional resistance between the pliant fibers is large and it tends to cause stretching of fibers having an extremely small Youngs modulus. Therefore, in these spinning systems, an elastic fiber can be carded or drawn only in the case where it is blended with a larger proportion of a hard fiber having a considerably high Youngs modulus in order to make the elastic fiber move together with the said hard fiber. In other words, the spinning of the elastic fiber is limited only to the case where the proportion of the elastic fiber is considerably low. In this connection, US. Pat. No. 3,007,227 discloses that in processing the fiber blends on conventional textile machinery, it has been found more practical to employ between l percent and 25 percent of the elastic fiber in the blend, although special equipment may be selected to more readily accommodate broader ranges of the elastic fibers. If the proportion of the elastic fiber in the blend is raised, sufficiently beyond 30 percent, fiber processing operations into yarn become more difficult to control and the resulting yarn and fabric quality suffers: for example, when 50 percent elastic fiber is used.

A direct spinning system employed for the manufacture of the present spun yarn of elastic fiber is described below in conjunction with the drawings.

In FIG. 1, multifilament yarn 2 released from bobbin 1 is fed, via a pair of rolls 6,6 to a breaking zone A, and is stretch-broken between said back rolls and a pair of intermediate rolls 7,7 the surface speed of rolls 7,7 being to times faster than the speed of rolls 6,6. Thereby, a mass of broken and transformed fibers 3 is then sent to the subsequent draft zone B, in which it is drafted to a desired count yarn between intermediate roll 7,7 and front rolls 9,9 having a surface speed several times faster than that of rolls 7,7. The fleece 4 comes out of the front rolls 9,9 and is passedthrough a pig tail l0, twisted to a desired twisting condition by means of revolving spindle l2, and wound, via ring and traveller 11, on a cop as spun yarn 5. If the elastic fiber a is to be blended with a hard fiber, roving 14 of hard fiber is released from another bobbin 13, passed over a guide roll 15, and fed to the intermediate rolls 7,7 and blended therein with the elastic fibers 3. In another method, after passing over the guide roll 15, said roving 14 of hard fiber is fed to cradle 8 and blended with the elastic fiber therein. Some of the conventional direct spinning machines may possess a gear with edges in the breaking zone A, or a floating control roll and a single apron as a substitute for cradle 8 in the draft zone B. However, the principal action of these modified machines on the fiber is the same as that of the machine shown in FIG. 1. When the total denier of elastic fibers in the draft zone is too coarse and therefore a considerably high draft ratio is required to draw them to a desired yarn count, the already described difficulty of sliver drawing also occurs here. Therefore, it is desirable to adjust the draft ratio in the breaking zone so that the draft ratio in the subsequent draft zone is less than 10, preferably less than 5.

Although spun yarn of elastic fiber can be prepared by using the conventional direct spinning machine illustrated in FIG. 1, it is difficult or impossible to obtain as good quality yarn, as will be obtained if the special pretreatment described hereinafter is applied to the elastic fiber. It is most preferable to employ the direct spinning machine equipped with the special apron apparatus of the present invention as shown in FIG. 4.

The first reason why it is difficult to obtain a good quality yarn with the machine shown in FIG. 1 is as follows: As compared with a hard fiber having smaller breaking elongation and poor recovery from stretching, the elastic fiber used for the preparation of the present spun yarn possesses at least 100 percent breaking elongation and quick recovery from stretching to an elongation which is less than its breaking elongation. In order to obtain spun yarn having such excellent elasticity using the elastic fiber and to prevent yarn breaking strength from being reduced by slipping between fibers in the yarn, it is necessary to employ a fiber of at least 0.5 inch minimum length, more than 1 inch average length and 3 inches as the preferable average length. When the average length of the fiber exceeds 4 inches and the total denier of the fiber is coarse, the drawing operation in the draft zone is quite difficult to carry out. Since the breaking elongation of spandex fiber, for example, is in general in the range of 400 800 percent, the broken length of the fiber will be about 20 inches (3 inches X (5 9)) considering the fiber length under no load as being 3 inches. In this connection, the distance (gauge length) between the back rolls 6,6 and the intermediate rolls 7,7 will be determined by using the following equation:

wherein D is draft ratio; ho is the distance between back roll and intermediate roll, a is the breaking elongation of elastic fiber and L is the stretched fiber length which has been forwarded by the intermediate roll until it is broken. Taking the conditions of e 6 and L 20 inches, the correlation between he and D is shown in FIG. 2. (Correctly speaking, L plus one half ho should be 20 inches, but for the sake of simple calculation L is taken as 20 inches) According to FIG. 2, even a large draft ratio of 20 gives only a narrow roll distance of about 2.6 inches in the case of a 3 inch fiber length. If the average free length of the fiber is less than 2 inches, this roll distance will be much smaller than that of the above case. Therefore, in the direct spinning system shown in FIG. 1, approximately one thousand ends of fibers must be distributed in a relatibely small breaking zone. As already described, the elastic fiber possesses a large frictional resistance acting between fibers, so that the end of a fiber tends to be forwarded with the movement of the end of another fiber thereby causing a number of ends to be simultaneously caught by the intermediate roll, and stretched and broken in the breaking zone. That is, an evenly spun yarn can not be obtained in this method. Indeed, the above may be avoided by further widening the roll distance to give a considerably larger distribution of fiber ends, but it may also result in the necessity of employing a longer fiber length, (e.g., providing ho 4 and D 20, free fiber length should then be 4 inches as shown in FIG. 2), which in turn causes a different problem in the draft zone as previously stated.

Therefore, one solution concerning the present invention for obtaining a better quality yarn with the direct spinning machine as shown in FIG. 1 is to subject the elastic fiber to a heat-setting treatment prior to feeding it into said machinery. That is, the elastic fiber is heat set while in a stretched state to reduce its breaking elongation and increase its Youngs modulus. For example, if the elastic fiber is previously modifiedto have 200 percent of breaking elongation, a fiber having a 3 inch free length should be broken at a stretched fiber length of 9 inches (3 inches X 3). In this case, from the abovesaid equation, ho will be 4.1 inches when D is 20. This condition means a good distribution of fiber ends. Furthermore, a longer free fiber length such as 4 inches can be successfully employed, because the fiber has a high Youngs modulus, so that little trouble is found in the drawing step in the draft zone. In this case, he is 5.4 inches, so that it gives a quite favorable distribution of fiber ends. Spun yam thus prepared from the pre-treated fiber possesses a high Youngs modulus and low breaking elongation. However, this spun yarn may conveniently be converted to the state in which it hasthe original properties as possessed by the unmodified elastic fiber, by subjecting the yarn to a relaxation treatment under free loading conditions (for example, in skein or in the form of woven fabric or knitted fabric) in boiling water or a steam box. This recovery may be Somewhat influenced by the stretching ratio and heating temperature employed in the pretreatment, but almost complete recovery can be obtained. Some of the test results in the case of spandex fiber is shown in the following Table l.

rolls 34 are adjusted so as to permit slippageof the stretched fiber before breaking. The stretched elastic fiber is further advanced while slipping to the intermediate rolls 31,31, where it is nipped by rolls 31,31, stretched in a desired draft ratio and broken. After passing through the rolls 31,31, the stretch-broken elastic fiber immediately shrinks by its own elasticity to a pre-determined free fiber length, and the thus obtained fiber 24 is, while being carried on the bottom apron 35, sent to cradle rolls 36,36 and drafted to a desired count fleece 25 in the draft zone provided be tween the cradle rolls 36,36 and front rolls 38,38. This fleece 25 is then passed through pig tail 39, twisted by rotation of the spindle, and wound, via ring and traveller 40, on cop 41 as a spun yarn 26. As is clear from the above,'the elastic fiber in the stretch-breaking zone i tretshesifsl y y a P i effes moving me TABLE 1 Material After pro-treatment After free relaxation Breaking Breaking Breaking elongation, Youngs elongation, Youngs Treating elongation, Youngs percent modulus Treating conditions percent modulus conditions percent modulus 80 C. b0il. 515 50 400% stretch, 80 0., 10 min. steam set 320 155 100 C. b0il 680 43 800 65 120 C. steam. 790 40 80 C.boil 390 100 400% stretch, 100 0., 10 min. steam set 250 240 100 C. boil 510 60 120 C. steam 690 45 REM.\RK.Youngs modulus shows the Value of tension gram in 250% extension of 530 d. spandex multifilament yarn.

The second reason why a good quality spun yarn is hard to obtain by the direct spinning machine as shown in FIG. 1 is hereinunder described.

The elastic fiber employed in the present invention possesses a quick recovering property from various degrees of stretching, so that the fiber ends which are broken in the stretch-breaking zone spring back to form hock ends. These hock ends not only obstruct the even drawing of the fiber, but also often get entangled with an adjacent fiber to obtain its movement as a single fiber, and cause many fibers to be stretched and broken simultaneously. In this case, as shown in FIG. 3, it is preferable to employ a pair of endless aprons 16,16 placed between the back rolls 6,6 and the intermediate rolls 7,7 and driven at a speed which is faster than the surface speed of the back rolls 6,6 and slower than the surface speed of the intermediate rolls 7,7, to prevent the spring back of broken fiber ends and, to reform the hock ends of the fiber if such occurs.

In order to obtain the best quality spun yarn of elastic fiber, it is recommended to employ the direct spinning machine as shown in FIG. 4. In this figure, the area between back rolls 29,29 and intermediate rolls 31,31 is the stretch-breaking zone A, and the area between the intermediate rolls 31,31 and front rolls 38,38 is the draft zone B. Multi-filament yarn 22 of elastic fiber is released from bobbin 21, passed through back rolls 29,29, and introduced via tensors 30,30 into the clearance between top apron 33 and bottom apron 35, these aprons being driven by intermediate rolls 31,31 and rotating with a surface speed several times faster than that of back rolls 29,29. The elastic fiber having a large breaking elongation is thus stretched by means of faster moving aprons 33 and 35. The clearance between the top tensor and the bottom tensor 30 and the resilient action of adjustable spring 46 forthe press means and fed to the intermediate rolls 31,31 as it is. Therefore, the fiber length being forwarded by the intermediate rolls before the fiber is brought to its breaking elongation, is considerably small and almost the same as that of hard fiber. Consequently, it is possible to select and fix the distance between the back rolls and intermediate rolls over a considerable size. Furthermore, by controlling the pressure of springs 46 on press rolls 34 and the clearance between the top and the bottom tensors 30,30 it is possible to change the extent of stretch and the position of slippage of the fiber placed between the aprons 33,35. Therefore, the breaking point can be concentrated in a desired position or distributed throughout the apron, and the fiber length can be controlled in any desired size. These are exemplified in FIG. 5. When the elastic fiber is stretch-broken in such a way, the spring back of the fiber end can be effectively controlled by the top and bottom aprons, so that no problems are caused in this regard as compared with the case using the machinery as shown in FIG. 1. Thus, a better quality yarn can be spun in accordance with this invention.

When it is required to prepare a blended spun yarn of elastic fiber and hard fiber, the same apparatus as shown in FIG. 4 is conveniently employed with a slight modification thereon. That is, another roving 43 consisting of hard fiber alone is released from another bobbin 42, passed over guide roll 44 and blended with elastic fiber 24 at the cradle rolls 36,36. For convenience in varying the blend ratio or yarn count, it is possible to place rolls 45,45 in a position between the guide roll 44 and the cradle roll 36 so that the hard fiber roving 43 is drafted by the surface speed difference between the rolls 45,45 and the cradle rolls 36,36. However, since it is difficult to place some apparatus for controlling floating short fibers the roving in the position be:

tween, the cradle rolls 36,36 and the rolls 45,45, the draft ratio in this area must not exceed 5, the preferable draft ratio being 1 to 3.

In this type of blending system,-mixing of each fiber is in general not so good. However, the spun yarn has elasticity and these characteristic properties are brought by the elastic fiber employed. Therefore, the elastic fiber is apt to be concentrated in the center of the yarn and the hard fiber will be distributed at the periphery, and thus complete mixing of the fibers is unnecessary in this case.

When it is required to give high elasticity to the blended spun yarn, this may be accomplished by adjusting the clearance between the top and the bottom tensors 37,37 of the cradle in the draft zone B, such that the elastic fiber can be nipped (however, slippable on the brink of breaking) and the hard fiber can be slipped therebetween. Thus, by adjusting the clearance between the tensors, any elastic spun yarn having from O to more than 100 percent of elasticity may be prepared at will.

Aswill be clearly understood, the present spun yarn of elastic fiber can be easily prepared by using the methods and the apparatus described hereinabove.

The present spun yarn of elastic fiber is a distinctive product and differs from any of the known spun yarns of hard fibers. The following are the reasons therefor.

Firstly, spun yarn containing 30 percent to 100 percent by weight of an elastic fiber having more than 100 percent elastic elongation, extremely small Youngs modulus and excellent quick recovery from various degrees of stretching to an elongation less than its breaking elongation, has never been prepared, though filament yarn of elastic fiber has been heretofore known.

As mentioned above, the present spun yarn of elastic fiber is hardly prepared or can not be prepared at all by merely using a conventional spinning system, and in order to obtain a better quality spun yarn it is necessary to modify the elastic fiber beforehand by giving a special heat-set treatment thereto or to employ a modified direct spinning system equipped with a certain device. That is, in case of a hard fiber, its spun yarn is obtained as a matter of course by using any conventional spinning system or conventional direct spinning system, so far as its filament yarn exists. However, in the case of an elastic fiber, it is not the same as that in the case of hard fiber to obtain its spun yarn, even if its filament yarn exists.

Secondary, since elastic fibers possess an extremely small Youngs modulus, the fibers in the twisted spun yarn stick to one another to cause a considerable frictional resistance between the fibers, and therefore when such a spun yarn is stretched, there hardly occurs any slipping between the fibers. To the contrary, in the case of a hard fiber, in order to maintain a satisfactory yarn tensile breaking strength, the spun yarn must be comprised of more than 50 ends of fibers. if the fiber the effective coefficient of fiber strength in yarn strength (i.e., yarn tensile strength single fiber strength x fiber number in cross section of yarn) to 100 percent, the mean value being 50 to 60 percent and the maximum value being 70. Contrary to the above, in a spun yarn of an elastic fiber, no decrease in the yarn strength is detected for the abovesaid reasons even in a product having as few as fiber ends in the cross section of spun yarn, and'the effective coefficient of fiber strength in yarn strength is almost lOO percent. in this regard, the correlation between the effective coefficient and the fiber number in the cross section of yarn is shown in FIG. 6, wherein (a) represents the curve for an elastic fiber and (b) the curve for a hard fiber. From these curves, it will be seen that the minimum fiber number in cross section of the present spun yarn to maintain the yarn strength is quite different from the corresponding value of the conventional hard spun yarn, and that the maximum effective coefficients are quite different from each other.

Thirdly, when fibers are stretch-broken in a direct spinning system, there is a great difference between an elastic fiber and a hard fiber in their respective stretchnumber in the cross section of the yarn is less than 50 breaking phenomenon. That is, in the case of a hard fiber, though the maximum fiber length may be controlled by using a particular breaker, it is impossible to prevent the occurrence of short fibers, the minimum fiber length thereof being about several mm, for the following reasons. Namely, the breaking of the fiber occurs throughout the breaking zone, and since the breaking elongation (e, in the aforesaid equation) of hard fiber is less than 0.4, and in general is 0.2 0.3, the L value becomes almost zero. On the contrary, in the case of elastic fibers, the breaking elongation of the fiber is in general 400 800 percent and therefore 5 is in a range between 4 and 8 and L can be a considerably larger value. Thus, in the present spun yarn of elastic fiber, the minimum fiber length is quite long as compared with the case of hard fiber and the short fiber content is extremely small as a result.

The following examples will serve to illustrate the spun yarn of elastic fiber, the preparation thereof and the useful effects obtained by this invention.

EXAMPLE 1 Employing a multi-filament yarn (5000 d/SOO fil.) of spandex elastic fiber having 300 percent breaking elongation, 0.2 g/d Youngs modulus (stress in percent extention), and 98 percent recovery from lOO percent extention, pure spandex spun yarn of 400 d having 40 ends of fiber in cross section was obtained by using the direct spinning machine as shown in FIG. 4, under the following conditions.

Stretch-breaking zone draft ratio l0 distance between back roll and intermediate roll 9 inch Draft zone draft ratio L2 twist 26 T/inch Employing the same conditions as state above, except that the draft ratio in the draft zone is increased to 3.4, another pure spandex spun yarn of (1 having 15 ends of fiber, and 31 T/inch was prepared. The mechanical propertiesof these two spun yarns are shown in Table 2.

TABLE 2 Pure spun Material Pure spun yarn (400 d.) yarn (150 d.)

After boiling in order to relax strain Multiimposed durfilament After ing spinning yarn spinning process After spinning Yarn denier (d.) 5,000 400 420 150 Break ng strength (g.) 2,300 210 260 68 Break ng strength (g./d.) 0. 45 0. 53 0.65 0. 45 Breaking elongation (percent) 300 160 295 130 Youngs modulus:

(L/d. 50% extension (L/d. 100% extension KgJmm.

As clearly seen from the above Table 2, the breaking elongation of spun yarn after spinning decreased and the Youngs modulus slightly increased compared with that of multifilament yarn, because the elastic fiber is subjected to the stretch-breaking treatment. However, as a result of the after boiling treatment, such as dyeing, the inner structural strain of the fiber was removed and the said breaking elongation and Youngs modulus were restored to the normal conditions. However, the Youngs modulus of the thus after-treated yarn was slightly lowered compared to that of the original material filament yarn. It might be due to the twists in the finished spun yarn. Even in the spun yarn constructed with ends of fibers, the breaking strength (g/d) was almost identical with that of material filament yarn. Thus, the effective coefficient of fiber length in yarn strength was 100 percent.

EXAMPLE 2 Pure spandex spun yarn (400 d, 26 T/inch S twist) prepared by the method of Example 1, was employed as a core yarn and an acrylic fiber roving (fiber denier 2 d, fiber length 2 inches) was used as a sheath fiber. Stretching the core yarn with a draft ratio of 2, corespinning was carried out. The thus obtained core-spun yarn possessed 40 percent of elastic fiber content, 22 Nm (metric count) of yarn count (i.e., corresponding to 410 d), and 12.2 T/inch of Z twist. Since the twist direction of pure spandex spun yarn was S while the twist direction of core-spinning was Z, the twisting torques of the yarn disappeared. The kink number of the thus prepared core-spun yarn was 26 and this product was found to be useful for the following knitting or weaving process. For the sake of comparison, similar core-spinning was carried out with non-twist filament yarn (210 d) of elastic fiber and acrylic fiber roving, and consequently the kink number of core-spun yarn obtained was 52. This core-spun yarn had to be steam set to decrease the kink number to for the subsequent process. 7

EXAMPLE 3 Employing the direct spinning machine shown in FIG. 4, a multi-filament yarn (5000 d/500 fil.) of spandex elastic fiber having 300 percent breaking elongation, 0.2 g/d (stress in 100 percent extention) Youngs modulus, and 98 percent recovery from 100 percent extention, was stretch-broken in the stretch-breaking zone under the conditions of 7.45 draft ratio and 9 inches distance between the back roll and intermediate roll. Another roving consisting of 2 d fiber denier, 2 inches fiber length acrylic fibers having 0.1 g/m sliver weight, was continuously fed to the cradle roll in the draft zone, and blended with the elastic fiber coming from the stretchbreaking zone. Then the blended yarn was drawn with a draft ratio of 2.24 to give a desired yarn count of l/l3 Km (metric count), twisted (23 twist/inch) by revolution of the spindle and wound up on a cop. The breaking strength and the breaking elongation of this product were 683 g and 107 percent, respectively. After subjecting the product to free relaxation in boiling water, these values changed to 558 g and 277 percent. The spun yarn obtained by this Example comprised 43 percent spandex fiber and the remainder was hard fiber. Excellent elasticity and good recovery from stretching were found for the spun yarn (after spinning) within the limit of 50 percent extention and on the relaxed spun yarn (after relaxation in boiling water) within the limit of 150 percent extention, respectively.

The term elastic fiber used herein refers to the synthetic fibers having elasticity due to construction with soft segment and hard segment such as spandex fiber having a urethane group as a bonding group or the fibers having urea group or acid amide group as a bonding group, and includes fibers formed by extruding or cutting natural rubber or synthetic rubber. Therefore, this elastic fiber has the following characteristic mechanical properties.

more than l00% (generally 400-80092) breaking elongation (generally 0.030.l g/d) Youngs modulus wherein the elastic recovery from high stretching is indicated by the percentage of recovered stretch to the net stretched length of the fiber just after being stretched to of the breaking elongation thereof, kept for one minute, and then released from stretching and the Youngs modulus represents the stress when the fiber is percent extended.

The term hard fiber" used herein refers to fibers having less than 50 percent breaking elongation, and including natural fibers such as cotton, wool, linen, jute and silk, regenerated cellulosic fibers such as viscose, cuprammonium, and acetate, and synthetic fibers consisting of homopolymers such as polyamides, polyacrylonitrile, polyesters, polyvinylchloride, and polyvinylalcohol, or consisting of copolymers thereof.

The present invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

What is claimed is:

1. Apparatus for preparing spun yarn of 100 percent elastic fiber or blended spun yarn of elastic fiber and hard fiber, said apparatus comprising: a back roll means for feeding fiber from a supply thereof, a front roll means spaced from said back roll means for drafting fiber received therefrom, a stretch breaking zone and a draft zone arranged in succession in that order between the back roll means and the front roll means, an endless bottom apron means extending between the back roll means and front roll means over the stretch breaking zone and the draft zone, respective plates adjacent the back roll means and front roll means supporting the bottom apron means at the opposite ends thereof, output roll means in said stretch breaking zone for drawing fiber from said back roll means and stretch breaking said fiber, input roll means in said draft zone for receiving fiber from said output roll means and advancing the fiber to said front roll means, said output roll means including top and bottom rolls for advancing 0nd top apron means in said draft zone, each of the first and second top apron means having a respective input and output, two further plates, one adjacent the back roll means and the other adjacent the front roll means, said first top apron means including a first endless top apron member passing on said one further plate and the top roll of said output roll means in said stretch breaking zone and driven by the latter, said second top apron means including a second endless top apron member passing on said other further plate and the top roll of said input roll means in said draft zone and driven by the latter, said first and second top apron means being opposed to said bottom apron means to control the feed of the fiber therethrough, and means to adjust the pressure applied by the top apron member in the stretch-breaking zone to the bottom apron member.

2. Apparatus as claimed in claim 1 comprising means for feeding roving from a second supply directly to the input rolls means in said draft zone.

3. Apparatus as claimed in claim 1 comprising a second input roll means for feeding a second fiber to said input roll means in said draft zone, said second input roll means and said input roll means in said draft zone having different surface speeds to form a second draft zone which is distinct from the first draft zone.

UNITED I STATES 'PATEN 'II OFFICE I CERTIFICAT-E ()F CORRECTION Patent No. 7 ,4 Dated February 5, 1974 I Hiroshi Nakano et a1.

Inventor-(s) v I II I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the coversheet insert [30] Foreign Application Priority Data I I I Japan 43692/1966 July 6, 1966 Japan 43693/1966 July 6, 1966 Signed I and sealed this. 24th day of September 1974. I

(SEAL) Attest: II I McCQY M. GIBSON JR. c. MARSHALL. DANN Attesting Officer Cumin-loner .of Patents FORM PO-OSO (PU-(59) 

1. Apparatus for preparing spun yarn of 100 percent elastic fiber or blended spun yarn of elastic fiber and hard fiber, said apparatus comprising: a back roll means for feeding fiber from a supply thereof, a front roll means spaced from said back roll means for drafting fiber received therefrom, a stretch breaking zone and a draft zone arranged in succession in that order between the back roll means and the front roll means, an endless bottom apron means extending between the back roll means and front roll means over the stretch breaking zone and the draft zone, respective plates adjacent the back roll means and front roll means supporting the bottom apron means at the opposite ends thereof, output roll means in said stretch breaking zone for drawing fiber from said back roll means and stretch breaking said fiber, input roll means in said draft zone for receiving fiber from said output roll means and advancing the fiber to said front roll means, said output roll means including top and bottom rolls for advancing the fiber therebetween, saiD input roll means including top and bottom rolls for advancing the fiber therebetween, said bottom apron means including an endless apron member which extends on and is driven by the bottom rolls of said input and output roll means, a first top apron means in said stretch breaking zone, a second top apron means in said draft zone, each of the first and second top apron means having a respective input and output, two further plates, one adjacent the back roll means and the other adjacent the front roll means, said first top apron means including a first endless top apron member passing on said one further plate and the top roll of said output roll means in said stretch breaking zone and driven by the latter, said second top apron means including a second endless top apron member passing on said other further plate and the top roll of said input roll means in said draft zone and driven by the latter, said first and second top apron means being opposed to said bottom apron means to control the feed of the fiber therethrough, and means to adjust the pressure applied by the top apron member in the stretch-breaking zone to the bottom apron member.
 2. Apparatus as claimed in claim 1 comprising means for feeding roving from a second supply directly to the input rolls means in said draft zone.
 3. Apparatus as claimed in claim 1 comprising a second input roll means for feeding a second fiber to said input roll means in said draft zone, said second input roll means and said input roll means in said draft zone having different surface speeds to form a second draft zone which is distinct from the first draft zone. 